EXERCISE TRAINING-INDUCED INCREASE IN CORONARY TRANSPORT CAPACITY

The objective of this study was to measure effects of exercise trainin g on coronary flow heterogeneity, microvascular transport, and hemodyn amics. Five miniature swine were trained on a treadmill (ET) for 16 wk ; five control pigs (C) were confined to cages for the same period. At the end of that period we used the multiple indicator dilution method to measure permeability-surface area product (PS) to EDTA over a rang e of now (F) in an anesthetized, open-chest preparation. We found that the heterogeneity of now as measured by microspheres decreased with i ncreasing F, but that ET had no clear effect on heterogeneity. We eval uated PS from the indicator concentration curves, taking into account flow heterogeneity and variations in capillary recruitment throughout the bed. In both C and ET pigs we observed an increase in PS with F un til a maximum value of PS was reached at full recruitment. This relati onship between PS and F was unaltered by ET. However, hemodynamic resi stance was significantly reduced by ET, and F was higher at a given pe rfusion pressure after training. Since PS increases with F, ET pigs ha d higher PS values at typical coronary artery pressures.